CZ27325U1 - Anion-selective membrane of block polymer reinforced by glass fibers with polymer coating - Google Patents

Description

Anion-selective block copolymer membrane reinforced with glass fiber with polymer coating

Technical field

The invention relates to a membrane for alkaline membrane electrolysis for the production of hydrogen. Electrolysis can be performed at higher pressures because of the direct compression of the generated hydrogen.

BACKGROUND OF THE INVENTION

Water electrolysis is a process in which water is converted directly to hydrogen by electrical energy. Although water electrolysis is not a widespread process, it has a number of advantages: the whole process takes place in a single step, the hydrogen produced is very high in purity, the process produces zero emissions, the equipment can be both large-volume and highly compact the water mentioned here, which is a huge supply on Earth, which is not consumed in the process, but is temporarily converted to hydrogen. The disadvantage of water electrolysis is the cost of the hydrogen produced, which is higher compared to fossil fuel processing processes. For this reason too, efforts are being made in the field of water electrolysis to reduce the energy consumption of this process.

At present we divide water electrolysis into alkaline, acidic (so-called PEM) and high-temperature, which is still rather in the research and testing phase. Alkaline electrolysis, on the other hand, is the oldest and the only industry-wide technology for water electrolysis. This is due to its simple, well mastered and above all cheap construction, which is based on the use of highly available materials that are stable in the (alkaline) environment. The electrodes are made of nickel or nickel-plated steel (the cathode may be steel) and the diaphragm is predominantly asbestos. Alkaline electrolysers operate with hot (80 ° C) hydroxide (25 to 30 wt%). Compared to acid electrolysis, however, alkaline electrolysis suffers from several drawbacks. The main ones are higher operating costs (higher operating voltage at the same current densities) and larger dimensions, which is also due to the asbestos diaphragm used, which does not have optimal parameters in this respect, is relatively thick, non-ionic, does not allow zero-gap electrode arrangement and last but not least it is carcinogenic.

Acid water electrolysis, on the other hand, has more compact dimensions and, above all, more favorable operating characteristics (lower operating voltage). The problem of acid electrolysis is the need to use expensive platinum catalysts since the only ones are stable in the environment and at the same time sufficiently catalytically active. This precludes the use of acidic electrolysis of water in large-scale industrial production and is thus directed towards mobile applications. In PEM electrolysis, a perfluorinated cation exchange membrane (predominantly Nafion®) with sulfone functional groups is used as the electrolyte. A great advantage of this membrane is its high temperature stability at very low thickness. However, for the membrane to be active, its hydration and subsequent swelling are required, which is guaranteed by the circulation of demineralized water inside the cell. The operating temperature of the PEM electrolysers is 80 to 90 ° C.

The impossibility of zero-gap electrode arrangement and higher working voltages at the same current densities was due to the absence of a sufficiently stable and ion-conducting ionomer from which an anion exchange membrane could be made. In recent years, however, an ionomer has been developed which allows the preparation of a membrane with the desired properties. However, this ionomer lacks excellent mechanical resistance, as is the case with some cationselective membranes, especially sulfonated perfluorinated membranes. In recent years, efforts have been made to conduct the process at elevated pressure due to the direct compression of the generated gases, saving energy that would have to be spent on additional compression of a significant amount of gases.

-1 CZ 27325 Ul

The essence of the technical solution

The above-mentioned problems with mechanical stability of the anionelective membrane have been solved by reinforcing them with Teflon and glass fibers. In this case, the glass fibers are responsible for the increased mechanical resistance of the resulting composite membrane, but unfortunately these glasses corrode strongly in the alkaline environment. The function of the anionelective membrane is the transport of anions in strongly alkaline environment, where the positive charge is fixed on the backbone. For this reason, the actual anionselective ionomer cannot be in contact with the reinforcing glass fibers. This would result in a gradual elution of ions from the glass material itself, which would result in a gradual embrittlement of the glass, after which it would eventually collapse its structure and the glass fibers would cease to perform its function as a fitting. Thus, the glass fibers must be protected from the alkaline environment by a substance which allows good adhesion of both the glass and the anion-selective polymer itself.

Thus, the membrane itself consists of fiberglass CAS 65997-17-3, which is provided with a coating consisting of polytetrafluoroethylene CAS 9014-83-9, hereinafter referred to as PTFE. A reinforcing PTFE coated glass fiber skeleton is located at the center of the anion selective ionomer membrane. The anionselective ionomer consists of a polystyrene-block-poly (ethylene-ran-butylene) -block-polystyrene backbone CAS 66070-58-4 with a tetramethylammonium CAS 51-92-3 backbone.

Example of technical solution implementation

Example 1

The membrane for the electromagnetic membrane electrolysis according to this solution contains in wt%:

15,4 fiberglass CAS 65997-17-3,

4.6 polytetrafluoroethylene CAS 9014-83-9, an anionic ionomer consisting of polystyrene-block-poly (ethylene-butylene) -block polystyrene CAS 66070-58-4 with tetramethylammonium functional groups CAS 51-92-3,

Σ 100.0.

The membrane exhibits at a temperature of 30 ° C transverse ionic conductivity of 5.6 S.M ^'1, which at 50 ° C rises to 7.4 S.M ^-1 and at 70 ° C rises to 7.9 Sm ^first The diaphragm allows operation with a pressure difference of 550 kPa.

Example 2

The membrane for the electromagnetic membrane electrolysis according to this solution contains in wt%:

13,3 fiberglass CAS 65997-17-3,

7.7 polytetrafluoroethylene CAS 9014-83-9, an anionic ionomer consisting of polystyrene-block-poly (ethylene-butylene) -block polystyrene CAS 66070-58-4 with functional groups consisting of tetramethylammonium CAS 51-92-3,

Σ 100.0.

The membrane exhibits at a temperature of 30 ° C transverse ionic conductivity of 5.6 S.M ^'1, which at 50 ° C rises to 7.3 Sm ^-1 and a temperature of 70 ° C increases to 7.9 S.M' ^first The diaphragm allows operation with a pressure difference of 360 kPa.

Example 3

The membrane for the electromagnetic membrane electrolysis according to this solution contains in wt%:

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9.2 Glass fiber CAS 65997-17-3

10,8 polytetrafluoroethylene CAS 9014-83-9, an anionic ionomer consisting of polystyrene-block-poly (ethylene-butylene) -block polystyrene CAS 66070-58-4 with functional groups consisting of tetramethylammonium CAS 51-92-3,

Σ 100.0.

The membrane exhibits at a temperature of 30 ° C transverse ionic conductivity of 5.2 Sm ¹ which at 50 ° C rises to 7.3 Sm ^-1 and a temperature of 70 ° C increases to 7.5 S.M ^'first The diaphragm allows operation with a pressure difference of 240 kPa.

Example 4

The membrane for the electromagnetic membrane electrolysis according to this solution contains in wt%:

8,7 fiberglass CAS 65997-17-3,

11,3 polytetrafluoroethylene CAS 9014-83-9, an anionic ionomer consisting of polystyrene-block-poly (ethylene-butylene) -block polystyrene CAS 66070-58-4 with tetramethylammonium functional groups CAS 51-92-3,

Σ 100.0.

The membrane exhibits at a temperature of 30 ° C transverse ionic conductivity of 5.1 S.M ^'1, which at 40 ° C rises to 7.1 S.M ^-1 and at 70 ° C rises to 7.2 S.M' ^first The diaphragm allows operation with a pressure difference of 120 kPa.

Example 5

The membrane for the electromagnetic membrane electrolysis according to this solution contains in wt%:

19,25 fiberglass CAS 65997-17-3,

5.75 polytetrafluoroethylene CAS 9014-83-9, an anionic ionomer consisting of polystyrene-block-poly (ethylene-butylene) -block polystyrene CAS 66070-58-4 with tetramethylammonium functional groups CAS 51-92-3,

Σ 100.0.

The membrane exhibits at a temperature of 40 ° C transverse ionic conductivity of 4.1 S.M ^'1, which at 60 ° C rises to 4.9 S.M ^-1 and at 70 ° C rises to 5.2 S.M' ^first The diaphragm allows operation with a pressure difference of 570 kPa.

Example 6

The membrane for the electromagnetic membrane electrolysis according to this solution contains in wt%:

23,1 fiberglass CAS 65997-17-3,

6,9 polytetrafluoroethylene CAS 9014-83-9, an anionic ionomer consisting of polystyrene-block-poly (ethylene-butylene) -block polystyrene CAS 66070-58-4 with tetramethylammonium functional groups CAS 51-92-3,

Σ 100.0.

The membrane exhibits a transverse ion conductivity at 30 ° C of 3.2 S.m ^-1 , which at 40 ° C rises to 3.7 S.m ^-1, and at 70 ° C it rises to 4.1 S.m ^-1 . The diaphragm allows operation with a pressure difference of 610 kPa.

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Industrial applicability

The membrane with an anionic selective polystyrene-block poly (ethylene-ran-butylene) -block-polystyrene backbone polymer, which is functionalized with tetramethylammonium and reinforced with glass fibers coated with polytetrafluoroethylene, is suitable for alkaline membrane electrolyzer.

Claims (1)

PROTECTION REQUIREMENTS Membrane for alkaline membrane electrolysis, characterized in that it contains in wt%: 8,7 to 23,1 glass fibers CAS 65997-17-3, 4,6 to 11,3 polytetrafluoroethylene CAS 9014-83-9, 70 to 80 polystyrene-block-poly (ethylene-ran-butylene) -block-polystyrene CAS 66070-58-4 with tetramethylammonium functional groups CAS 51-92-3, sum of glass fibers CAS 65997-17 -3, polytetrafluoroethylene CAS 9014-83-9 and 15 polystyrene-block-poly (ethylene-ran-butylene) -blockpolystyrene CAS 66070-58-4 with a tetramethylammonium CAS 5192-3 functional group reaching 100% The resulting membranes exhibit a transverse ion conductivity at 30 ° C of 3.2 to 5.6 Sm ^-1 , at a temperature of 40 ° C of 3.7 to 7.4 S.m ^-1 and at 70 ° C a transverse ion conductivity a conductivity of 4.1 to 7.9 Sm ¹ , these membranes allowing to work at a pressure difference of 120 to 610 kPa depending on the content of glass fibers and polytetrafluoroethylene.